It’s a well-known factoid that batteries keep getting cheaper while capacity increases. That said, as with any market that is full of people who are hunting for that ‘great deal’, there are also many shady sellers who will happily sell you a product that could be very dangerous. Especially in the case of large LiFePO4 (LFP) batteries, considering the sheer amount of energy they can contain. Recently [Will Prowse] nabbed such a $125, 100 Ah battery off Amazon that carries no recognizable manufacturer or brand name.
If this battery works well, it could be an amazing deal for off-grid and solar-powered applications. Running a battery of tests on the battery, [Will] found that the unit’s BMS featured no over-current protection, happily surging to 400 A, with only over-temperature protection keeping it from melting down during a discharge scenario. Interestingly, under-temperature charge protection also worked on the unit.
After a (safe) teardown of the battery the real discoveries began, with a row of missing cells, the other cells being re-sleeved and thus likely salvaged or rejects. Fascinatingly, another YouTuber did a similar test and found that their (even cheaper) unit was of a much lower capacity (88.9 Ah) than [Will]’s with 98 Ah and featured a completely different BMS to boot. Their unit did however feature something of a brand name, though it’s much more likely that these are all just generic LFP batteries that get re-branded by resellers.
What this means is that these LFP batteries may be cheap, but they come with cells that are likely to be of questionable quality, featuring a BMS that plays it fast and loose with safety. Although [Will] doesn’t outright say that you shouldn’t use these batteries, he does recommend that you install a fuse on it to provide some semblance of over-current protection. Keeping a fire extinguisher at hand might also be a good idea.
I mean, if you have a garden, you could dig a pit, concrete-line it and place all that stuff into it.
Totally secure.
You mean, move it straight to landfill? That’s pretty much the best thing to do with a lot of the garbage that Amazon ships nowadays, from vendors with names that look like a cat walked over a keyboard. “Hmm shall I buy the battery pack from JOUTKFR or from TUJNWOO? Both have identical pricing and product photography but the former has dozens of 5* reviews saying it’s a great box of disposable rubber gloves…”
Enjoy paying the brand-name tax, I guess. It all comes from the same factory in Guangzhou anyways. Plus if it doesn’t work, returns are free, subsidized by the people who buy expensive equipment with English names :^)
Is it “brand-name tax” to receive what’s written on the label? At least if I ordered from the factory in China they’d be honest. If I order from random fly-by-night company it’s pure gambling.
The brand-name tax must meet with certain requirements that must be met. These no name brands failed those requirements. That’s why it’s so cheap. You are not getting something for nothing. Now if the no name brand meets your requirements, that’s fine.
A brand name is no guarantee of a product meeting stated specs, particularly with batteries. Specs are used as a marketing point and they are competitive. You’d be hard pressed to find any battery that meets it labelled AH or WH rating. I only know this because I was part of a team that evaluated batteries for a large PC vendor. Most other componenents and systems are rated the same way.
Specs are never based on typical performance or long term performance (unless so stated). They are some best case number used for marketing and should be considered as such. Make sure you get a detailed spec from a vendor and you’ll know what you’re getting, otherwise you’re a victim of marketing.
Finally, I’ve found that if a product on Amazon doesn’t meet what was stated, you can typically get your money back if you complain and I suspect the vendor won’t profit.
That’s going to be a problem when it rains. Additional measure will need to be taken.
I’m optimistic.
https://hackaday.com/2025/06/15/making-corrugated-cardboard-stronger-and-waterproof/
No kidding, a friend once did that for his garden house which was solar powered.
He built an small underground battery bunker made of concrete, with a door, a lock and everything.
But he used traditional, proven-by-time lead-gel batteries (sealed&maintenance free), no fancy LiFePO.
A good clear fire exit is going to be a lot more likely to save you than a fire extingusher if one of these large batteries goes up in flames. I mean a fire extinguisher is always a good idea, but I wouldn’t count on it for a lithium fire. Better to chuck a fire blanket over the battery, run for it and call the fire brigade.
I would suggest building and housing the batteries in small above-ground outdoor structure that is at least a few meters away. A modified water-tight case with buried conduit may be sufficient.
A fire extinguisher will be no use on a battery pack. But may stop the fire spreading.
Fire blanket is the preferred option – fire services locally have have apparently started using huge ones for cars.
Go find Will Prowse’s video ” LFP Battery Fire Safety: What You NEED to Know” where he explains that LiFePO4 batteries are considered very safe, especially when compared to other lithium-ion battery chemistries. They are thermally stability and resistant to thermal runaway, the phenomenon that causes other lithium-ion batteries to overheat and potentially catch fire.
They are effectively as flammable as wood. They will burn, but not like the Lithium Polymer batteries you’ve seen burning like thermite.
Still, a clear fire exit and extinguishers and fire blankets are a good idea in any home, with or without batteries of any sort.
Don’t LiFePO4’s tend to light on fire a lot less? Like that’s why BYD can compensate for the lower power density with banks of prismatic cells?
Lifepo4 is less likely to burn, but not by much. Lion as used by the bicycle and scooter people, whole different story.
and that’s assuming these are really lifepo4…
The voltage is different so it’s hard to disguise any other battery type as lifepo4.
Isn’t it inherently a lot safer because the fire is not self sustaining (ie. It doesn’t reach thermal runaway) and you have to keep adding heat to keep the fire going?
Will Prose has done a video on LiFePO4 safety. Piotrsko could not be more wrong. To make LiFePO4 burn you have to put them into a fire and wait for the electrolyte to leak out. And it’s electrolyte that will burn, not the battery. LiFePO4 is far safer than driving around with a metal can of fuel bolted under your car.
The car is much safer than you’d expect. Both in theory and in practice when looking at what usually burns in a petrol car.
Liquid requires thermal energy to vaporise and the vapour is the dangerous form. Liquid is just liquid. And diesel might not be that dangerous even in vapour form. Gasoline vapour is the dangerous stuff.
And actually it is plastic can. Next to a hot exhaust.
Yes very safe compared to others. The problem is the wiring used to connect the battery to the inverter. If the amps exceed the wire ratting the wires heat up can cause a fire. Not a huge deal just put a 100 amp fuse on the wire, well properly size the fuse to the battery, and your okay. Also properly size the wires from your battery to the inverter and do a test. Feel the wires and make sure they are not getting hot if they are then you know you’ve got a problem somewhere.
If you want less-fire-prone or easier-to-put-out-a-fire batteries, at least consider non-Lithium solutions. Sure, they make take up more room and may have more mass, but if it’s for your off-grid shack out in the boondocks or even your house, the space-vs-safety trade-off may be worth it.
LiFePO4 is not like regular Lithium Ion in regards to chemical fire. As for arc and high amperage, you would want a good battery monitor circuit and proper fuse.
It’s not just a safety thing. Flooded lead-acid is very pricey right now – at least for quality gear. I’ve got a battery of Century-Yuasa cells, 1320ah/32kWh when new, but they’re approaching retirement age, and a new set is about AUD$19,000. I can get equivalent, quality LiFePo for a lot less than that.
Lead-gel batteries are more modern and friendlier than lead-acid.
Essentially same technology, but gel type doesn’t leak as easy.
They’re very longlived also and need no maintenance (by the user).
They still have safety vents for emergency so that gas can escape if overpressure occurs.
All in all a very friendly technology, considering that lead is involved.
And because it’s sealed, the risk for environmental damage is kept at a minimum.
Some info (not affilated):
https://www.ufinebattery.com/blog/gel-battery-vs-lead-acid-a-detailed-comparison/
https://www.batteriesplus.com/blog/power/sla-battery-venting
Lead-gel batteries are like twice the price of flooded lead acid and still have many of the same shortcomings.
LiFePO4 is a far better technology for home power storage. From round trip efficiency to life span. LiFePO4 is significantly better in nearly every metric. The biggest issue is they can’t be charged below freezing, that is easily solved by putting them in the heated part of your home or buying models that have built in heaters.
The biggest issue with lead based batteries is that you can’t use more than 50% their rated capacity without significantly impacting their working life. You will never get more than 2 or 3 years out of them if you go beyond 50%. So to start with you need nearly twice as much battery capacity in Ah at a particular voltage as you would need with LiFePO4. Not to mention lead batteries are bigger and way heavier.
In the long term LiFePO4 is a fraction of the cost of lead based batteries. Between the life span, useable capacity, shipping cost, etc… Even the premium LiFePO4 batteries are cheaper than Lead-gel in up front cost at this point.
Hi. Good points. To my defense, I didn’t think about money, but about reliability and safety.
On the positive side, lead batteries can endure alot of stress.
They can handle a high current surge, which is why they’re still used in uninterruptable power supplies (UPS).
In CB and amateur radio, lead-gel batteries can power the linear amplifiers in same way a car battery can.
For gel batteries, you don’t need an intelligent charger, either.
An 12v incandescent lamp in series to the power source can act as a charging controller. That makes it EMP safe. For example.
LiFePO batteries by contrast are nothing without an active, microcontroller operated power regulator.
The sheer number of people in the world who will fall for something like this unbelievable.
But, then again, a really spot-on saying is, “There are too many people who don’t have a real job.”
Rather hard to know when you don’t have hands on in advance (or even if you do with how often all these things are sealed up) what you are going to get, or these days what the going rate should be as there are far to many things making prices wildly fluctuating.
So saying folks ‘fall for it’ is perhaps a bit unfair.
Don’t worry, natural selection keeps care of the problem here. ;)
THis is a timely article. I’m considering replacing my dad’s wheelchair AGMs with LiFePo4 equivalents…
For safety and reliability reasons, I would suggest looking into sodium-ion cells. Cheap LiFePo4 batteries generally have a poor reliability. They are a bit more expensive and only medium density but a single mishap is more costly.
There may be better ones but here’s a sodium-ion cell: https://www.motawillbattery.com/26700-sodium-ion-battery-3-1v-3300mah-na-ion-cell/ (note the 10 year warranty)
Interesting, but I motice it is more than twice the volume for perhaps 10% more capacity than a Li-Ion 18650 cell for example. Of course for Solar you might want to investigate a lead acid setup anyway, both for reasons of cost and safety. Also Lead Acid batteries have a very robust recycling loop, the lead is very easy to reclaim and make into new batteries. I believe the Acid can be reclaimed as well.
Thanks for this info. I was looking for a drop-in replacement for the standard UB12220 AGM form factor that would be a little more tolerant of my parents’ abuse (overcharging followed by deep discharge) and would use the current charger circuitry in the wheelchair. The LiFePo4 battery I found meets all the requirements if (IF!) the very generous BMS stats can be believed.
As an SWL/CBer who eventually wants to try out 12v lead-gel accu alternatives,
I’d rather get some Emerit rechargeables from here in Germany.
According to the website they’re offering LiFePO4 accus with UN38.3/IEC62133 certification and a warranty.
Better safe than sorry. Such high-power-density batteries are like dynamite.
There have been great deals on Renogy LiFePO4 batteries on Amazon if you wait for the “deals”
Save it to your shopping list and check regularly, I just saved $55 on a 12v 100Ah LFP by Renogy
Renogy is the closest you will get to Battleborn LFP’s on a budget 😁
LFP cells are quite safe. They don’t catch fire by thermal runaway and most of the time not even on a dead short. Yes, once on fire it burns just as well as any lithium cell. But people sleep well in the same building with large gas tanks or nearly a ton of propane in their backyard…
I have a self-made LFP battery 4S2P with each 100Ah in my off-grid solar powered cottage and I’m cautious, yet confident about its safety :)
Weirdly, some LFP batteries have different ‘rest’ voltages. Some LiFePO4 chemistries are more equal than others, it seems.
I have several LiFePO4 batteries of various capacities, from an ancient Bioenno brand, to my most recent “ERYY” brand. That most recent one, labeled as “23.5 Ah” measures in at 25.0 Ah, but weirdly has a lower terminal voltage than all the others. Its internal BMS terminates charge at 13.7 V (it goes open circuit), full charged it is 13.6 V, 80% charge it rests at 13.2 V and at end-of-charge it falls off the cliff at 12.0 V. It’s otherwise a good power source. Its BMS disconnects the load at 30A, but it’s still a solid 12.0V at that current.
This is quite different from all my other ones, that charge right to 14.6V (limited by the chargers), fully charged rest at 14.1V and 80% around 13.7V. They also fall off the cliff at 12.0V.
I can’t find any mention of alternate LiFePO4 chemistries that can explain the different voltage.
At a low charge current, 3.4v gets a lifepo4 cell above 90% charged. Sounds good for cell longevity.
You should always install your own fuse anyway. If nothing else, it is easier to replace than one built into a battery. Of course, don’t replace it until you’re sure you’ve fixed what made it blow.
Been following Will for years back when he lived in an RV. You would do very well following his advice. He really knows his subject matter.